The present invention relates to small, high precision, multicore optical guides and to their production process.
The present invention more particularly applies to the production of very economic, monomode, optical guides, but can also be applied to the production of multimode optical guides.
Certain types of multicore optical guides are already known from the following documents:
"High density multicore-fibre cable": S. Inao and Al. in Proc. 28th int.--Wire and cable symp.--November 1978.
"New type of multicore fibre"--Proc. DFC--April 1982: N. Kashima and Al.
"Analysis and experiments with crosstalk between adjacent graded-index optical fibres"--J. lightwave Technol.--Vol. LT3--August 1985.
In addition, FR-A-2,510,545, entitled "Process for the preparation of a multiple optical fibre" describes a means for drawing elementary cylindrical blanks in order to group them in an assembly of elementary optical fibres by filling the spaces between the fibres by introducing an intermediate liquid material consisting of at least one compound chosen from among the oxides forming glassy networks, oxides modifying glasses and intermediate oxides. This process is intended to prevent the formation of bubbles on drawing.
FR-A-2,551,881 and FR-A-2,551,885 describe processes for the production of a multicore optical fibre, particularly by the partial, but directional disappearance of the core of the blank, thus making it possible to separate the two cores of the future optical fibre.
These documents
either only describe the principle of multicore guides and in particular multimode multicore guides,
or stress the disadvantages of said guides with regards to marking and precision without obviating these disadvantages,
or describe processes leading to a simple assembly of fibres, which in no way solves the problem of the great accuracy necessary for connecting these guides under economic conditions, the problem of marking or registration and the problem of obtaining a limited size leading to a maximum densification,
or describe processes which lead e.g. to two cores in a small volume, but in no way lead to guides of high quality and with the necessary geometrical precision.
None of these documents leads to easily markable, high precision multicore guides, with a view to a simple and effective connection, or having small dimensions in order to bring about a real densification of optical fibre cables e.g. usable for transmitting information to subscribers of a telecommunications network.